The head of ASIO has defended comments on terrorism that angered the One Nation party and caused concern in the Coalition.

ASIO director-general Duncan Lewis faced heavy criticism from One Nation after telling the party’s leader Pauline Hanson last week that the refugee program is not the source of terrorism in Australia.

One Nation senator Malcolm Roberts tweeted that “If ASIO can’t see a link between refugees and terrorism we are in far greater danger than I thought”.

The issue also flared in the Coalition party room meeting yesterday and the Attorney-General has organised for Mr Lewis to brief Government MPs on the issue.

Today Mr Lewis has defended his position, saying tens of thousands of refugees have come to Australia over the last decade or so “and a very few of them have become subjects of interest for ASIO and have been involved in terrorist planning”.

Mr Lewis has conceded that three fatal terrorist attacks in Australia in recent years have involved either refugees or the children of refugees.

“I am not denying that … but context is very important, the reason they are terrorists is not because they are refugees but because of the violent extremist interpretation of Sunni Islam that they have adopted,” the ASIO head told RN.

Mr Lewis said they were radicalised by viewing online material while very young in their loungerooms and bedrooms, “absorbing this brutal material”.

He defended Australia’s refugee program, saying screening measures are adequate and the border control regime is very sound.

Former prime minister Tony Abbott has accused him of tiptoeing around the issue, but Mr Lewis rejected any criticism.

“I am not here to vilify the Islamic community. I am here to keep the Australian community safe and ASIO works very hard every day on that particular issue,” he said.

But he warned it is not possible to prevent all attacks, saying 12 attacks have been thwarted since September 2014, but four had succeeded.

“That indicates we have very good arrangements to do background checking and prevent would-be terrorists from plying their trade but it is not foolproof,” Mr Lewis said.

Of the 12 terrorist attacks thwarted, he said 11 were being planned by young men who were radicalised in the spirit of this “Sunni Islamist extremist cult” and one was a a right-wing extremist who had nothing to do with Islam.

– ABC